The 3rd Generation Partnership Project (The 3rd Generation Partnership Project, “3GPP” for short) is a leading 3G technical specification organization with the purpose of studying, formulating, and promoting 3G standards that is based on an evolved GSM core network.
An access network discovery and selection function (Access Network Discovery and Selection Function, “ANDSF” for short) is a functional entity formulated by 3GPP in an evolved packet core network (Evolved Packet Core, “EPC” for short), and the ANDSF is used to assist a user terminal (User Equipment, “UE” for short) in discovering and choosing to be connected to a non-3GPP network such as Wi-Fi or WiMAX. A structural diagram of a deployment of the ANDSF is shown in FIG. 1: A UE exchanges information with an ANDSF server through an S14 interface by using IP layer communication. When the UE is in a home public land mobile network (Home Public Land Mobile Network, “HPLMN” for short), the UE only needs to acquire an operator policy from a home ANDSF (“H-ANDSF” for short). When the UE is in a visited public land mobile network (Visited Public Land Mobile Network, “VPLMN” for short), the UE may establish a connection to the H-ANDSF or a visited ANDSF server (“V-ANDSF” for short) or both, to acquire an operator policy. Acquiring an operator policy by a UE includes the following three steps: discovery of an ANDSF server, establishment of an ANDSF security link, and acquiring of an operator policy.
There are three main manners for the discovery of an ANDSF server (that is, acquiring of an IP address of the ANDSF server): 1. Home operator configuration, which may be used for an H-ANDSF; 2. Dynamic Host Configuration Protocol (Dynamic Host Configuration Protocol, “DHCP” for short) query, which may be used for an H-ANDSF; 3. Domain name system (Domain Name System, “DNS” for short) query, which may be used for both an H-ANDSF and a V-ANDSF.
The establishment of an ANDSF security link is mainly as follows: The UE and the ANDSF server perform two-way authentication (GBA-based) of a pre-shared key (Pre-Shared Key, “PSK” for short) and a Transport Layer Security protocol (Transport Layer Security, “TLS” for short), to establish a security link connection between the UE and the ANDSF. If the UE does not support the security mechanism, a security mechanism stipulated in Open Mobile Alliance-Device Management (Open Mobile Alliance-Device Management, “OMA-DM” for short) needs to be used to ensure link security.
The acquiring of an operator policy mainly includes two modes: a Pull mode and a Push mode. The Pull mode means that the user terminal actively initiates a query to the ANDSF server, to acquire a related operator policy; the Push mode means that the ANDSF server sends prompt information (such as SMS) to the user terminal, the user terminal establishes a connection to an ANDSF according to the prompt information and initiates an information query, and the UE initiates an information query request to the ANDSF by using Generic Alert information of OMA DM. The UE and the ANDSF use an ANDSF management object (Management Object, “MO” for short, which is an OMA-DM MO) to carry operator policy information, so as to exchange information.
An ANDSF mainly provides the following three kinds of information for a UE: 1. An inter-system mobility policy (Inter-system mobility policy, “ISMP” for short), where the policy mainly provides a network selection policy for a user terminal that cannot simultaneously support multimode transmission (such as LTE and Wi-Fi); 2. An inter-system routing policy (Inter-system routing policy, “ISRP” for short), where the policy mainly provides a network selection policy for a user terminal that can simultaneously support multimode transmission (such as LTE and Wi-Fi); 3. Network discovery information (Discovery Information), where the information provides a list of available networks, which is based on a user terminal location, for the user terminal, and the list includes access information of each network, so as to assist the user terminal in being connected to the network. Each ISMP and ISRP have a corresponding valid restriction, which includes a user terminal location (including a physical location, a cell location, or the like) and time. A user terminal selects an operator policy with a highest priority from all valid operator policies (when priorities of all valid operator policies are the same, a visited operator policy is prior to a home operator policy; if all valid operator policies belong to a same priority and a same operator, a decision is made based on implementation).
Wi-Fi Alliance (Wi-Fi Alliance) was founded in 1999, aiming at improving interoperability between wireless network products that are based on the IEEE 802.11 specifications. A Subscription MO mechanism is a management mechanism proposed by the alliance for managing Wi-Fi users' account information and an operator policy (a network access policy). A deployment structure of the Subscription MO is shown in FIG. 2: A UE is connected to a service operator network by using a Wi-Fi access network (a Hotspot network), exchanges account information on an OSU server, and exchanges operator policy information on a policy server. Before a user exchanges with these servers, a mutual authentication message needs to be forwarded by an Authentication, Authorization and Accounting (Authentication Authorization Accounting, “AAA” for short) server of the Hotspot network to an AAA server of the service operator, so as to perform two-way authentication, and then the UE can exchange information with the OSU server or the policy server by using a Hypertext Transfer Protocol over Secure Socket Layer (Hypertext Transfer Protocol over Secure Socket Layer, “HTTPs” for short) technology. The UE and the OSU server or the policy server use a Subscription MO to carry user account information and operator policy information, so as to exchange information. The operator policy mainly includes a list of visited service providers (with priorities) that are recommended by an operator for access and a list of visited service operators that are prohibited by the operator.
The following scenario may occur in the prior art: A UE roams to a remote area and enters an operation scope of an operator, but the UE is not a subscriber of the operator. For some reason (for example, expensive 3GPP tariff), the UE is not connected to a 3GPP network of the operator (therefore, the UE cannot establish a connection to an ANDSF server of the operator to acquire a policy of the operator), but the UE determines to be connected to a network of the operator by using Wi-Fi, and finds, by means of scanning, that the operator leases multiple Wi-Fi access points provided by multiple Wi-Fi service providers. In this case, the UE randomly selects an access point of the multiple Wi-Fi access points because the UE does not know a network access policy of the operator. As a result, the selection may be inconsistent with the network access policy of the operator (that is, the access point selected by the UE is not an access point that the operator expects the UE to select). The UE acquires the network access policy of the operator after the UE visits the network of the operator by using the access point. In this case, if the access point selected by the UE is not the access point that the operator expects the UE to select, the UE exits the access point that is selected previously, and reselects an access point according to the acquired policy.
The foregoing network access process is low in efficiency.